<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
'<h1>结果</h1>'
'<h2>hello {{ fullname }}</h2>'
'<h3>aeiou 出现的内容有 {{ letters_result }}</h3>'
</body>
</html>